1. Field of the Invention
The present invention relates to a 3,4-dihydro-2H-benzopyran derivative of general formula (I) ##STR1## wherein R.sup.1 is a hydrogen atom or a lower alkyl group; R.sup.2 and R.sup.3 are the same or different and each is a hydrogen atom, a lower alkyl group or a lower alkoxy group, or R.sup.2 and R.sup.3 taken together represent a group of the formula --CH.dbd.CH--CH.dbd.CH--; R.sup.4 is a hydrogen atom or a hydroxy-protecting group; A is a group selected from the class consisting of --CH.sub.2).sub.n, phenylene, --CH.sub.2 SCH.sub.2 --, --CH.sub.2 CH.sub.2 SCH.sub.2 --, --CH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 --, --CH.sub.2 S--SCH.sub.2 --, --CH.sub.2 CH.sub.2 S--SCH.sub.2 CH.sub.2 --, --CH.sub.2 SCH.sub.2 SCH.sub.2 --, --CH.sub.2 CH.sub.2 SCH.sub.2 SCH.sub.2 CH.sub.2 --, ##STR2## where n is an integer equal to or greater than 1; R.sup.5 and R.sup.6 are the same or different and each is a hydrogen atom or a lower alkyl group or taken together represent a group of --(CH.sub.2).sub.4 --; R.sup.7 and R.sup.8 taken together represent ##STR3## R.sup.9 is a hydrogen atom or a lower alkyl group and X is a halogen atom, and a method of producing said 3,4-dihydro-2H-benzopyran derivative.
In further aspects, the present invention relates to a method of using a compound of the above general formula wherein R.sup.4 is a hydrogen atom, i.e. a 3,4-dihydro-6-hydroxy-2H-benzopyran derivative of the following general formula (I') as a stabilizer for organic materials and an organic composition containing the same stabilizer. ##STR4##
2. Description of the Prior Art
The 3,4-dihydro-2H-benzopyran derivatives of general formula (I) as provided by the present invention are novel compounds which have not been described in the prior art literature. Among these 3,4-dihydro-2H-benzopyran derivatives, the compounds of general formula (I) wherein R.sup.4 is a hydrogen atom, that is the 3,4-dihydro-6-hydroxy-2H-benzopyran derivatives of general formula (I'), have excellent antagonistic and preventive actions against unfavorable effects due to heat, light and oxidative factors and are of use as stabilizers for organic materials sensitive to heat, light or/and oxidizing factors, such as oils and fats, waxes, pharmaceutical compositions and preparations, cosmetic products, rubber products, synthetic resins, etc. Moreover, the compounds of general formula (I) wherein R.sup.4 is a hydroxy-protecting group can be easily converted to those 3,4-dihydro-6-hydroxy-2H-benzopyran derivatives (I') possessing the aforementioned antagonistic and preventive actions by substituting a hydrogen atom for said protecting group in accordance with the per se conventional procedure.
Recently attention has been focused on vitamin E as a safe antioxidant but as it is comparatively expensive and ready to be oxidized and discolor, it has not been commonly employed for antioxidative purposes.